Because of their excellent mechanical characteristics, such as impact strength, and because of their excellent heat resistance and transparency, polycarbonates are widely used for various purposes. Known as processes for the production of the polycarbonates are processes which involve a direct reaction of aromatic dihydroxy compounds such as bisphenols with phosgene (interface processes), and processes in which aromatic dihydroxy compounds such as bisphenols and carbonic acid diesters such as diphenyl carbonate are allowed in molten state to undergo ester interchange reaction (polycondensation reaction).
In processes for the production of polycarbonates by ester interchange of aromatic dihydroxy compounds with carbonic acid diesters, the reactants are normally heated at a temperature of from 250.degree. to 330.degree. C. under reduced pressure and allowed in molten state to undergo the ester interchange in the presence of catalysts such as organic salts, inorganic salts, oxides, hydroxides, hydrides and alcoholates of metals. These processes are advantageous over the above-mentioned interface processes in that polycarbonates are produced in relatively low costs. These processes involving the reaction of the aromatic dihydroxy compounds with the carbonic acid diesters in molten state; however, the polycarbonates produced are generally poor in color tone, heat resistance or water resistance.
With a view of solving the problem we conducted extensive research and eventually accomplished the present invention on the basis of our finding that excellent heat resistance and water resistance can be provided by reducing terminal hydroxy groups of polycarbonates being formed by end capping them with specific compounds.